The crotch (or crotches) of non-metal pipe fittings such as tees, ells, 45° bends, crosses, wyes and double wyes is a common failure point when such fittings are subjected to cyclic pressure conditions. The crotch is acted on by the pressurized fluid and is induced towards becoming round or inverted.
Conventional attempts to mitigate these forces have frequently been based on adding material to the outside crotch area using big radii, ribs, tapers, etc. However, the additional material on the outside of the fitting does little to reduce stress in the crotches, and adding material to the outside of the fitting adds cost. In some cases such additional material can make stress in the crotches worse.
Other attempts to mitigate crotch stresses have been based on a reduction to the flow path diameter. Reducing the flow path diameter adds wall section and strength as well as reducing hoop stresses which the fluid applies to the fitting. However, reducing the flow path diameter increases the pressure drop across the fitting and requires unnecessary and costly additional material to portions of the fitting not subject to stresses.
Accordingly, there is a need for a reinforced non-metal pipe fitting which minimizes crotch stress failures while avoiding the aforementioned problems in the prior art.